As is known, systems for energy scavenging or energy harvesting from intermittent environmental energy sources (which supply, that is, energy in an irregular way) have aroused and continue to arouse considerable interest in a wide range of fields of technology. Typically, energy-scavenging systems are configured to harvest, store, and transfer energy generated by mechanical sources to a generic load of an electrical type.
Low-frequency vibrations, such as, for example, mechanical vibrations of disturbance in systems with moving parts, may be a valid source of energy. The mechanical energy is converted, by one or more purposely provided transducers (for example, piezoelectric or electromagnetic devices) into electrical energy, which can be used for supplying an electrical load. In this way, the electrical load does not require batteries or other supply systems that are cumbersome and present a poor resistance to mechanical stresses.
FIG. 1 is a schematic illustration of an energy-scavenging circuit 1 according to an embodiment of a known type. The energy-scavenging circuit 1 comprises a transducer 2, for example of a piezoresistive type, subjected to environmental stresses (signal SE), which generates a time-variable voltage signal VTRANSD. The energy-scavenging circuit 1 includes an energy storage circuit 4, for example a capacitor, configured to store the electrical energy transduced. The transducer 2 and the storage element 4 are coupled together by means of a diode 5. In use, the voltage VTRANSD (which, in general, does not necessarily has a sinusoidal waveform, but has a substantially random evolution) is received at input by the diode 5 which operates as peak detector. With reference to FIGS. 2a and 2b, the detection of a peak P1 of VTRANSD (above the conduction threshold of the diode 5) causes the transfer to the storage element 4 of a current ICHARGE that charges the storage element 4, saturating it. Any possible peaks P2, P3 of VTRANSD that have an amplitude smaller than the peak P1, and that follow the peak P1 do not concur in charging the storage element 4.
The above behavior of the energy-scavenging circuit 1 is not desirable.
There is a need in the art to provide a circuit and a method for adjusting the electric power supply for an environmental-energy-scavenging system that will be free from the drawbacks of the known art.